The long and short of it is the long and short of it. You need something in a longer barrel (6" or so), and a smaller one (J frame snubby). My personal favorite is a 19-5 6", in terms of balance and accuracy; I personally find the 6" 686 nose-heavy, though many swear by it. I second the advice about clustering calibers; with one exception (a Model 29), all of my Smith wheelguns can take 38 cal. By far the cheapest to shoot.
That brings up the other question alluded to: do you want to be a shooter, or a collector? The two markets are very different. In fact, I would say they barely overlap at all, since a collectible becomes a shooter if it is shot with any frequency. [Or, to put it another way, can you bear to spoil the pristine-ness of your newly acquired Model XX Nickel with powder residue and a turn line?] I personally wouldn't want a gun I wouldn't shoot, so the fact that my 19-5 isn't "P&R" doesn't bother me; others really get a kick out of having something perfect that was made when craftsmanship mattered.